Drilling mud treating composition



DRnLrNo MUD TREATING COMPOSITION Edison G. Lee, Bellaire, Tex., assignorto Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware NoDrawing. Application April 6, 1949, Serial No. 85,935

8 Claims. (Cl. 252-85) This inventionrelates to additives for oil Welldrilling muds, and more particularly relates to an improved form ofquebracho extract characterized by improved storage properties and byimproved efficiency when used as a treating agent or additive in oilwell drilling muds.

Quebracho extract comprises the tannin-containing extract of thequebracho tree, which grows principally in Argentina and Paraguay, inSouth America. The normal commercial handling of the material includesthe extraction with Water or the like of the valuable constituents ofthe hardwood of the tree at substantially the site of cutting the tree,and the shipping of the hardened extract in solid form to grinding millsin this country. As received, the extract comprises substantially 80% to85% solids, the remainder being occluded water. Of the solids, from 70%to all of the solids, based upon the entire extract, may be soluble inwater and between 65% and 72% of the composition may be tannins.Non-tannin materials, such as lignins, tars, gums, cellulose, sugars,and starches, comprise the remainder of the soluble constituents and theWater-insoluble portion of the extract. Since the extract is a naturalproduct often produced under relatively primitive conditions, noabsolute quantitative analysis is available; in fact, the composition isvariable but generally remains within the limits set forth above.

Where the quebracho extract as imported is to be diverted to welldrilling uses, the same is ground and packaged by the recipient in thiscountry to prepare the extract for use in drilling mud treatment. Whileno great criticality characterizes the grinding with respect to ultimateparticle size, it is in general preferable and the practice in the artto grind to at least an extent that all of the material will pass a 10or 12 mesh to the inch screen, such as a U. S. standard No. 14 screen.Finer grinding is sometimes resorted to but coarser grinds are ingeneral not used since ultimate speed of solution is adversely modified.

After being ground and packaged, the quebracho extract is normallystored in the grinders warehouse until purchased by drilling mudchemical distributors or retailers who maintain storage Warehousesadjacent to well drilling operations. The quebracho extract is thenstored in the retail distributors warehouses until purchased by drillingoperators, who dissolve the ground extract for treatment of the oil welldrilling mud at the well site.

A difiiculty arises in this chain of processing, however, whichdifficulty appears after the grinding operation of the extract in thatespecially in humid climates and in the warm humid summer months, but toa considerable extent the year-round, the quebracho extract aftergrinding has a tendency to return to solid form to an extent that theground material may set up in solid, substantially insoluble form in aperiod of time as short as two weeks. Since normal marketing practice inthe drilling industry does not ordinarily permit movement of groundquebracho extract to the driller in times even approaching such shortperiods, amounts of extract from 10% to 50% of the total received at thedrilling site are commonly discarded as insoluble lumps in the course ofattempting to dissolve the same. This discarding of material at the wellsite is normally dictated by the prohibitive expense of returning thelumped, insoluble material to the grinder for retreatment and by theimmediate necessities of the activities at the well site. Particularlyin view of the relatively large quantities of quebracho extract whichmay be employed at one time in a single drilling operation, a saving ofany fraction of this discarded material is significant. For example,. adrilling mud system for a single well wherein the constituents of themud may vary widely but will in general depend upon the location of thewell and usually include, as is Well-understood in the art, natural orartificial aqueous clay suspensions, which may or may not be weightedwith barytes and a variety of other materials, may consist of as much as650 to 4,000 or more 42-gallon barrels of mud, depending upon the natureof the drilling operation and the character of the formation beingdrilled. While a great number of factors wellunderstood in the drillingart influence the amount of quebracho extract which will be incorporatedin such a system, in general from 0.5 to 20 pounds of extract per barrelof mud, to give an average of usually not over ten pounds of extract perbarrel in the entire mud system, may be combined with the mud in orderto give it the properties known in the well drilling art to be necessaryor desired.

It will be understood that in accordance with wellunderstood practice inthe drilling art, the quebracho extract referred to above as combinedwith the drilling mud is preferably treated with an alkaline material ofwhich any of lithium, potassium, sodium, rubidium, and cesium hydroxidesmay be used but of which sodium hydroxide or caustic soda is thecommonest example. The ratio of quebracho extract to caustic may varyover wide ranges in accordance with conditions met by the driller but,in general, between one-third and one and one-half parts of caustic toone part of quebracho extract are employed, a particularly suitablerange being one-half part to one part of caustic to one part of theextract.

Accordingly, in order to incorporate the quebracho extract and alkalineagent, such as caustic soda, with the mud, solubilizing of the quebrachoextract as received is necessary and Where insolubles are found in thematerial as received up to 50% thereof, a tremendous wastage and loss ofthis relatively difficultly obtained commodity has heretofore obtained.Moreover, even in the rare cases where return to the grinder of thesolidified material is possible from an economic standpoint, a loss inweight, probably due to loss in moisture, of up to 5% occurs, which lossis an economic waste as transportation costs must be paid thereon.

The present invention has as its principal object the provision of asimple, inexpensive method for obviating the recaking of the groundquebracho extract and the provision of a composition comprisingquebracho extract which remains in small particle size, solubleconditions for indefinte periods of time.

A further object of the invention is to provide a quebracho-containingmaterial suitable for use in well drilling operations in the manner ofthe quebracho extract as now used in Well driling operations but havingimproved properties thereover and possessing the principally importantproperty of not caking after grinding.

A further object of the invention is to provide a composition comprisingquebracho extract which shall be substantially completely soluble in arelatively short time in either hot or cold water, whereby the same maybe used under the extremely rugged conditions which not uncommonly existat well sites where the material is used in drilling operations.

Further objects and advantages of the invention will appear more fullyhereinafter in the course of a detailed description of the same.

The present invention contemplates a combination with quebracho extractin the course of grinding, or the mechanical combination with groundquebracho extract immediately subsequent to grinding, of alkali metallignosulfonates in amounts ranging between and 25% by weight of thequebracho extract and most suitably about The particle size of theground material may be as disclosed above. When quebracho extract is sotreated, either during the grinding or immediately subsequent thereto,the extract no longer sets up into a cake following its grinding, evenunder the most severe humidity conditions. As a result of the presentinvention, the quebracho extract comes to the drilling rig in a veryreadily soluble form, as it is still substantially as finely ground asit was at the grinding operation and is found to be more readily solublein both cold and hot water than untreated quebracho extract, whetherfinely ground or not.

Where the expression alkali metal lignosulfonate is used, it will beunderstood that any alkali metal lignosulfonate, such as lithium,sodium, potassium, rubidium, and cesium, may be employed and it willmoreover be understood that, particularly since the sodiumlignosulfonate is normally recovered from paper manufacturingoperations, the sodium compound in general will be preferred both forsimplicity in use and for economic reasons. Highly refined alkali metallignosulfonates may be used but since they appear to add nothing to theefficient operation of the invention, relatively crude lignosulfonatesare in general preferred. Thus, the sodium lignosulfonate may berecovered from weak solutions in paper manufacturing operations; aparticularly satisfactory material for the purpose of the presentinvention has been found to be spray-dried or drum-dried sodiumlignosulfonate recovered from such solutions.

A particular advantage arising from the employment of the combination ofthis invention lies in the speed with which the material will dissolvein cold water, as compared to the speed with which quebracho extractalone dissolves in cold Water. It is apparent that the sodiumlignosulfonate addition to the quebracho acts as a solubilizer for thequebracho extract itself; most or all of the insolubles normally presentin the quebracho extract become soluble and available for treating ofthe drilling mud.

As pointed out hereinabove in connection with the quebracho extractitself, the combination of this invention may also be combined with analkaline material, such as those mentioned and particularly causticsoda, for application to the mud. The same proportions mentionedhereinbefore are also applicable, viz. one-third part to one andone-half parts of caustic to one part of the composition of thisinvention, the range, i. e. one-half to one part of caustic to one partof the composition, of this invention being in general preferred. Theaction of alkaline materials in the systems under discussion iswellunderstood and since such action forms no part of the presentinvention, need not be further adverted to.

It is an added feature of the present invention that the combination ofquebracho extract and alkali metal lignosulfonate results in a mudtreating material having somewhat more advantageous properties withrespect to viscosity, initial gel strength, ten-minute or delayed gelstrength, and particularly water loss than quebracho extract itself.

Thus, the property of the quebracho extract solution when used intreating the mud, of reducing the viscosity of the mud, in order thatcuttings and other foreign matter may settle out of the mud in settlingpits, is enhanced by the addition to the quebracho extract of between 5%and 25% of sodium lignosulfonate, by a factor of the order of 5%. Thoughapparently a relatively slight improvement obtains in the etficiency ofthe material of this invention over quebracho extract itself, it will beappreciated that present in the composition of this invention is onlybetween 75% and of quebracho extract, as compared to in the purequebracho extract and that therefore, less of the quebracho extract plusthe alkali metal lignosulfonate is doing a somewhat better job withrespect to reducing the viscosity of the mud than is done by thequebracho extract itself. This advantage of the material over quebrachoextract itself is, of course, additive to the important advantage of thecombination which is the non-caking character of the combination and itseasy solubility, as pointed out above. An additional significance of theviscosity reduction by the use of the combination of this invention liesin the reduction of fluid friction in the drill pipe and the improvedwashing or cleansing action on the drill bit that a lower viscosityfluid will have.

Furthermore, the combination of between 5% and 25% of alkali metallignosulfonate, such as sodium lignosulfonate, with ground quebrachoextract has the added advantage of providing low initial gel strength inthe mud when the material is added to the mud in quantities rangingbetween 0.2 pound/bbl. and 20 pounds/bbl. of the material of thisinvention to mud. The low initial gel strength, of course, is understoodto be desirable in order that the mud shall be pumpable and haveadequate washing action on the drill bit. Moreover, it is thecharacteristic of muds used for this purpose that they shall have highergel strength at periods following their initial use in order that theymay adequately pick up and remove high specific gravity solids in thewell, suspend high specific gravity solids in the bore hole while themud is quiescent, and remove the same from the bore hole and depositthem in the settling beds. It is, of course, undesirable to have thesubsequent gel strength of the mud go so high as to prevent its beingpumped from the Well or to cause dangerous swabbing of the hole. It hasbeen found that when quebracho extract itself, after suitable grindingand solubilizing, is added to mud on a basis to provide an ultimateratio of between 0.5 pound/bbl. and 10 pounds/bbl. of mud that thesubsequent ten-minute or delayed gel strength of the mixture isreasonably satisfactory. The material of the present invention, whensubstituted for straight quebracho extract, is similar in properties toquebracho extract itself with respect to gel strength, it beingunderstood that thereby a 5% to 25 saving in the amount of the extractnecessary for treatment of the mud is effected, and the extract thussaved is replaced by a material which is less expensive, is entirelydomestic, and contributes to the easy solubility of the extract inaccordance with the present invention.

Finally, it is found that the third significant property desired bydrilling experts to be found in a treated drilling mud, i. e. low waterloss, where water loss has reference to the seepage of water through themud cake or filter zones in the bore hole, is present to a significantlygreater extent in the material of the present invention comprising acombination of alkali metal lignosulfonate and quebracho extract than inquebracho extract itself. Thus, where heretofore quebracho extract aloneresulted in a water loss over a given period of time of the orderbetween 5 and 10 units, the combination of between 5% and 25% of sodiumlignosulfonate with the quebracho extract prior to solution and the useof such combination in mud in a ratio of between 0.2 pound/bbl. and 10pounds/bbl. of mud results in water loss of the order of 3 to 7 unitsbased on the same scale of measurement. It will be appreciated, aspointed out above, that this lower water loss is achieved while usingbetween 5% and 25 less of the quebracho extract.

Further advantages of the present invention are the absolute avoidanceof rcgrinding and consequent loss of weight referred to above and moresignificantly the fact that by combining quebracho extract with alkalimetal lignosulfonates, such as sodium liquosulfonate, in the course ofgrinding a solubilizing efi'ect upon the insolubles of prior artquebracho extract to an extent that insolubles of a tannin character, asreferred to above, are substantially eliminated and substantially all ofthe soluble material is therefore available as tannins for theirwell-known influence on the mud. Thus, a typical quebracho extractground with of sodium lignosulfonate contains 84.7% of total solids,78.6% of which is soluble and all of which is tannins and is thus madeavailable in the mud. The eifective increase in solubility, both byavoiding recaking and by making available more of the tannins present inthe extract, is an important feature of this invention.

In order that those skilled in the art may more fully be informed of theinvention, the following examples are oifered:

Example I Quebracho extract, as imported from the Argentine, is groundby a conventional grinding apparatus with one part by weight of sodiumlignosulfonate in powdered form being added to each nine parts ofquebracho extract ground. Subsequently the material is stored in groundcondition for a period of two and one-half months and thereafter isunpacked and found to be in a free-flowing state. This material isdissolved to make a solution comprising 12% thereof and 12% causticsoda. A natural drilling mud obtained from a drilling well was treatedwith the solution in the proportion of one part of solution to ninetyparts of mud. For comparison, ground quebracho extract containing nolignosulfonate was put in identical aqueous solution comprising 12%quebracho extract and 12% NaOH and the same natural drilling mud wastreated with the solution in the proportion of one part of solution toninety parts of mud. The tests showed the quebrachoextract-lignosulfonate compound produced a reduction of viscosity in themud slightly greater than the 100% quebracho extract solution alone; thereduction of gel strength was substantially the same with bothsolutions; and the water loss in the case of the quebrachoextract-sodium lignosulfonate composition was approximately 7.5% less.

The quebracho extract-sodium lignosulfonate composition was used totreat the drilling mud in the above-mentioned well until completion ofdrilling operations.

Example II Quebracho extract, as received from import, is ground in aconventional manner and subsequent to grinding, 10% of sodiumlignosulfonate in dry powdered form is intimately mechanically mixedtherewith. Thereafter, the material is stored for a period of threemonths, after which it is removed from storage and found to be in afreeflowing condition and ready for use in drilling mud treatment. Thismaterial was placed in solution and tests conducted on a naturaldrilling mud in comparison with identical ratio solutions containing100% quebracho extract. It is found that in accordance with standardtests of such treating materials, the resultant reduction of viscosityis comparable, as are the resultant reductions of gel strengths, whilethe water loss is improved by a factor of about 10% over quebrachoextract.

While there have been described various embodiments of the invention,the methods and products described are not intended to be understood aslimiting the scope of the invention as it is realized that changestherewithin are possible and it is further intended that each elementrecited in any of the following claims is to be understood as referringaii equivalent elements for accomplishing substantially the same resultsin substantially the same or equivalent manner, it being intended tocover the invention broadly in whatever form its principle may beutilized.

What is claimed is:

1. A dry, free-flowing, non-caking additive for drilling muds comprisinga mechanical mixture of dry ground quebracho extract and between 5% and25% by weight thereof of alkali metal lignosulfonate.

2. A composition as claimed in claim 1 wherein the alkali metallignosulfonate is sodium lignosulfonate.

3. A dry, freeflowing, non-caking additive for drilling muds comprisinga mechanical mixture of dry ground quebracho extract and 10% by weightthereof of sodium lignosulfonate.

4. The method of improving the solubility of quebracho extract andpreventing its caking after grinding, which includes grinding solidquebraco extract and substantially simultaneously mechanically mixingdry alkali metal lignosulfonate with said dry extract at least prior toresolidifieation of said extract after grinding.

5. The method of claim 4 wherein the alkali metal lignosulfonate issodium lignosulfonate.

6. The method of claim 4 wherein said alkali metal lignosulfonate issodium lignosulfonate recovered from paper-making operations.

7. The method of claim 4 wherein between 5% and 25% by weight of saidsodium lignosulfonate is employed.

8. The method of claim 4 wherein 10% by weight of said sodiumlignosulfonate is employed.

References Cited in the file of this patent UNITED STATES PATENTS940,394 Kumpfmiller Nov. 16, 1909 1,063,428 Gianoli June 3, 19131,563,010 Breedis Nov. 24, 1925 1,999,766 Lawton et a1 Apr. 30, 19352,109,858 Cannon Mar. 1, 1938 2,375,616 Booth May 8, 1945 2,450,936Cardwell Oct. 12, 1948 2,491,437 Perkins Dec. 13, 1949 2,505,818Williams et a1. May 2, 1950 2,560,930 Campise July 17, 1951 OTHERREFERENCES Salvesen et al.: Dispersants from Sulfite Liquor, article inChemical Industries, August, 1947, reprint, 3 pages.

1. A DRY, FREE-FLOWING, NON-CAKING ADDITIVE FOR DRILLING MUDS COMPRISINGA MECHANICAL MIXTURE OF DRY GROUND QUEBRACHO EXTRACT AND BETWEEN 5% AND25% BY WEIGHT THEREOF OF ALKALI METAL LIGNOSULFONATE.